As is well known it is necessary in vending food by an automatic vending machine to preserve frozen foods such as meat-buns and to heat them for sale.
However, since frozen foods take some time before they are completely cooked, it is difficult to prepare the necessary amount of food from frozen food in a short period of time, which hinders meeting the needs of both customers and vendors who desire to sale food in meal hours. This causes a big problem particularly in factories and offices.
Use of refrigerators instead of freezers relieves this problem somewhat in that refrigerated foods may be cooked in short time without being thawed. However, it is apparent that refrigerators cannot preserve foods in good condition for a long period as compared to freezers, thereby requiring frequent replenishment and tedious maintenance of food materials.
Japanese Patent Early Publication No. 1-237899 discloses a vending machine which stores a certain amount of already cooked food for sale based on a sale prediction. This machine may provides food quickly on demand. However, it cannot avoid deterioration of certain foods before sale.
A similar problem is encountered in a coffee vending machine which stores coffee materials and extracts coffee from the materials on an order made by a customer. In order to serve tasty coffee in such a coffee vending machine it is desirable to preserve coffee beans, instead of ground coffee materials. However, ground coffee has been only infrequently used in vending machine since grinding coffee beans and dripping coffee time is too involved and is consuming.
Coffee vending machines using ground coffee have an additional problem in that only a small amount of ground coffee may be stored in a vending machine, since ground coffee may be easily deteriorated, and hence it is difficult to preserve ground coffee fresh for a long time. Therefore, such coffee vending machines require frequent attendance for replenishment of fresh ground coffee.
It should be noted in the case of coffee vending machines, that coffee materials, no matter whether they are ground or not, oxidize very easily when they are exposed to the oxygen in the air, and humidity promotes deteioration. In order to prevent this undesirable change, coffee materials are usually preserved in evacuated containers or containers filled with nitrogen. However, it is not easy to maintain a vacuum or keep nitrogen in such a container under frequent use of the coffee. Consequently, these coffee vending machines are usually very complex in structure and are not suitable for vending a large amount of coffee.